1. Field of the Invention
The present invention relates to a display control apparatus that allows a plurality of input operations using a touch panel by a user, its control method, a program, and a computer-readable storage medium.
2. Description of the Related Art
Conventionally, various apparatuses and systems using an operation input means such as a touch panel have been developed and provided. With a development of applications that allows an intuitive input operation using a touch panel, user interface has been developed, and further advancement is expected from now on. Japanese Patent No. 3,181,181 discusses an operation determination method that allows a plurality of pen input operations without changing an input mode with respect to one application.
Further, a hand-written input is one of the characteristic input methods using a touch panel. When a control for an apparatus is performed based on such a trace of a touch position, a sampling method of the touch position may be important. Japanese Patent Application Laid-Open No. 2000-010721 discusses a technique for holding a balance between system load and the hand-written input operability by changing a sampling cycle to be an optimal value according to a changing speed of a touch position.
Further, there is provided a following function. That is, an operator quickly moves his finger in a certain distance while touching a touch panel, and then detaches his finger. A system control device of the touch panel detects this operation and moves the displayed item on the display panel, which is designated by the touch, with slowing down speed after the finger is detached (This operation is hereinafter referred to as flick). Japanese Patent Application Laid-Open No. 63-174125 discusses a technique in which a system control device scrolls an image displayed on a display unit by tracking a movement of a finger on a touch panel, gradually decreases the scrolling speed after the finger is detached from the touch panel, and stops the scrolling.
However, when a sampling cycle for detecting a touch position (coordinate) on a touch panel is slow, a system control device cannot distinguish a plurality of input operations, and thus an operability of the panel could be deteriorated. For example, there is a case that although a flick operation, in which an operator quickly moves his finger while touching, is performed, the system control device incorrectly determines that operation as a tap, in which a user touches on one point and quickly detaches without moving. Accordingly, for correctly distinguishing a plurality of input operations, a high-speed coordinate sampling is necessary.
However, when a system control device performs a high-speed sampling, load of a central processing unit (CPU) increases, so that an application performance may be decreased, such as a case that image display processing, e.g., animation processing, cannot be performed smoothly. Further, when the system control device always performs high-speed coordinate sampling processing, the number of analog digital conversion (AD conversion) processing is increased. Accordingly, power consumption is increased.